Beta-LPH is a polypeptide hormone of the anterior lobe of the pituitary, whose function in man is unknown although it has been shown to possess in vitro lipolytic and melanotropic activity. Within the beta-LPH molecule are contained the complete amino acid sequences of beta-MSH as well as of the enkephalins and endorphins. It has been shown that beta-MSH is an artifact and that "human beta-MSH" radioimmunoassays probably measure beta-LPH or related polypeptides. Using highly purified human beta-LPH and a specific antiserum prepared in the laboratory of Dr. C.H. Li, we have developed a sensitive and specific homologous radioimmunoassay suitable for measurement of beta-LPH in unextracted plasma. With this assay we plan to: 1) Measure plasma and cerebrospinal fluid beta-LPH in normal subjects and in patients with functional as well as apparently "nonfunctional" pituitary tumors both prior to and after heavy ion radiotherapy; 2) re-examine the close correlation between beta-LPH ad ACTH inferred from results obtained by "beta-MSH radioimmunoassays"; 3) re-evaluate, by in vivo studies in human subjects, the possible physiological significance of beta-LPH as a lipolytic hormone; 4) study the effect of hypothalamic releasing hormones, opiate receptor agonists and antagonists and of neurotransmitters on beta-LPH secretion; and 5) investigate the possible heterogeneity of beta-LPH in human plasma.